1. Field of the Invention
The present invention relates to a pad conditioner, a pad conditioning method, and a polishing apparatus, in particular, a pad conditioner which recovers a surface of a polishing pad in a polishing apparatus for polishing a work such as a semiconductor wafer, a polishing apparatus which is provided with the pad conditioner, and a pad conditioning method.
2. Description of the Related Art
As microstructure and multilayered structure of a semiconductor device have been achieved, CMP (Chemical Mechanical Polishing) technology has become essential in a manufacturing process of the semiconductor device. The CMP technology is now used for planarization of an insulating film between layers, as well as in various processes of Cu wiring and isolation, for example.
In the CMP technology for planarization, removal rate uniformity (polishing uniformity) across a work surface is an important specification. In order to improve the polishing uniformity, it is important to uniformly distribute any elements which affect the removal rate across a work surface.
While such important elements include a polishing pressure and a relative velocity in polishing, a surface state of a polishing pad is also an important element quantification of which is still in a preliminary stage. A preferable surface state of a polishing pad is achieved by conditioning the polishing pad. Also, a fact that, in a so-called in-situ conditioning in which a pad is conditioned during polishing, for example a stopping of the conditioning suddenly drops a removal rate, shows that a precise control of a surface state of a polishing pad is important.
Pad conditioning is an act to bring a pad conditioner having grinders such as diamond into contact with a polishing pad to scrape or roughen a surface of the polishing pad, so that a surface state of a new polishing pad is optimized as an initial state or the slurry holding capacity of the polishing pad in use is recovered to maintain its polishing capability.
Conventionally, pad conditioners having diamond abrasive particles electro-deposited thereto have been often used to condition a polishing pad by being pressed against the polishing pad while rotating around its central axis (for example, see Japanese Patent Application Laid-Open No. 2003-211355).
FIG. 7 shows a schematic view to illustrate a pad conditioner described in the Japanese Patent Application Laid-Open No. 2003-211355. The pad conditioner 130 described in the Japanese Patent Application Laid-Open No. 2003-211355 includes, as shown in FIG. 7, a substrate 131 having diamond abrasive particles 133 electro-deposited thereto, and a supporting section 132 to which the substrate 131 is fixedly attached.
In the pad conditioner 130, the tip ends of the diamond abrasive particles 133 are gradually abraded after repetition of pad conditionings, which in turn gradually reduces the conditioning capability of the conditioner 130, eventually leading to the end of its life. At the end of the life of the pad conditioner 130, the used substrate 131 having the abraded diamond abrasive particles 133 electro-deposited thereto is exchanged for a substrate 131 having new diamond abrasive particles 133 electro-deposited thereto.
In this case, the exchange of the used substrate for a new one 131 suddenly recovers the pad conditioning capability of the conditioner which will be again gradually lowered, and this generates an unpreferable behavior of the removal rate of a polishing apparatus which dramatically changes from a suddenly recovered level into a lower level over time, as shown by a dotted line of FIG. 4 which will be explained below. T1 and T2 in FIG. 4 show the timings for exchanging conditioner substrates.
In order to sustain this change, various pad conditioners and pad conditioning methods have been proposed (for example, see Japanese Patent Application Laid-Open No. 2004-001152). FIG. 8 is a schematic view to illustrate a pad conditioner described in the Japanese Patent Application Laid-Open No. 2004-001152.
The pad conditioner 120 described in the Japanese Patent Application Laid-Open No. 2004-001152 includes, as shown in FIG. 8, a plurality of conditioning pellets 121 having diamond abrasive particles electro-deposited thereto, and a base plate 122 to which each of the pellets 121 are removably and independently attached via a height adjusting device 124.
In this pad conditioner 120, the used conditioning pellets 121 can be individually exchanged for new conditioning pellets 121 depending on the abraded level of each conditioning pellet 121, so that a pad can be conditioned by the pad conditioner 120 with the used and new conditioning pellets 121 being simultaneously provided thereto.